Do your cold hydrogen valves have manual valves on the front and back?

We have hand valves at both the front and back here.

I’m also puzzled by this control valve assembly – there are no inlet and outlet valves; it seems they didn’t prepare for the possibility that the control valves might fail

What I have seen is that there is a check valve behind the control valve, as well as a manual valve; there is no manual valve in front of the control valve. I have also seen manual valves in front of control valves, as well as those with bypass lines; but in all cases it was a single manual valve

No, there is a check valve; the cold hydrogen valve is imported

There are no inlet or outlet valves, but there is a gate valve on the main pipe

There are two reasons for installing manual valves before and after the cold hydrogen valve: one is for maintenance purposes； II. Manual valves are involved in the control. In high-pressure hydrogenation environments, the risk associated with maintenance on dual valves remains high; therefore, manual valves are generally not used. Additionally, it is standard practice to equip control valves with handwheels, so that adjustments can be made manually in case of ordinary faults. For medium and low-pressure hydrogenation processes, if maintenance is taken into account, inlet and outlet valves can be installed; in my opinion, this isn’t a fundamental issue – it depends on the design philosophy. Both design approaches are valid, and it’s up to the owner’s management to decide which one to use! It depends on his production habits – if continuous production is desired, dual valves should be added; otherwise, it’s not necessary!

There is no manual valve, but the timing control valve can be operated manually on-site